For example, in the information recording medium, such as a CD and a DVD, as described in patent documents 1 and 2 or the like, there are developed a multiple layer or multilayer type, or dual layer type optical disc and so on, in which a plurality of recording layers are laminated or stacked on the same substrate. Then, in the information recording apparatus, such as a CD recorder, for recording information onto such a dual layer type (i.e. two-layer type) optical disc, the information is recorded into a recording layer (referred to as a “L0 layer” in this application, as occasion demands), located on the front or the closest side as viewed from the emission or irradiation side of laser light, in a rewritable method or irreversible change recording method by irreversible change recording heat by using heat or the like, by focusing the L0 layer with the laser light for recording. Moreover, the information is recorded into a recording layer (referred to as a “L1 layer” in this application), located on the rear of the L0 layer as viewed from the irradiation side of the laser light, in a rewritable method or irreversible change-recording method by irreversible change recording heat by using heat or the like, by focusing the L1 layer with the laser light through the L0 layer.
Moreover, in this type of optical disc or the like, the optimum power of a recording power is set by an OPC (Optimum Power Calibration) process, depending on the type of the optical disc and the type and recording rate of the information recording/reproducing apparatus, and so on. That is, the calibration is performed for the recording power. By this, it is possible to realize an appropriate recording operation which responds to variation in characteristics of the information recording surface of the optical disc. For example, if the optical disc is loaded and a writing command is inputted, data for test writing is recorded into an OPC area, with sequentially changing the optical intensity, so that a so-called “test writing process” is performed. In particular, according to the patent document 1, the OPC area is provided for each of the two recording layers, and a technology of performing the OPC process for each of the two layers is disclosed.
Patent document 1: Japanese Patent Application Laying Open NO. 2000-311346
Patent document 2: Japanese Patent Application Laying Open NO. 2001-23237